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Experts Agree: 165 MPH is a safe speed limit September 4, 2014

Posted by federalist in Transportation.

Safety is relative. There’s no guarantee you won’t be in a collision if you drive on public roads, no matter what precautions you take. So society, via engineers and legislators, weighs costs, benefits, and risks and reaches designs and compromises that are generally accepted.

But they are grossly inconsistent. Consider: America is full of roads with no physical divider and speed limits of 55 MPH. I.e., it is not considered excessively risky to drive 110 MPH relative to cars in adjacent lanes, separated by nothing more than a double yellow line. If you have ever designed, approved, or driven on one of these roads you evidently agree.

On a divided highway with a speed limit of 65 MPH this is equivalent to 165 MPH.

Many Americans to whom I have pointed this out seem appalled by the equation. What about distracted drivers? Can regular cars even handle such speeds? A small mistake at 65 MPH becomes catastrophic at 165 MPH.

Amusingly, on the unrestricted sections of the German Autobahn the answers to those questions are on display every day. For one thing, every modern road vehicle has a speed limiter (a.k.a. governor) set by its manufacturer to ensure that it isn’t pushed faster than its design limits. Drivers who push their cars well into triple digit speeds don’t do so without care. And distracted drivers, knowing that they share the road with aggressive drivers in high-performance cars, learn quickly to stay out of the left lanes. Of course they have accidents there too, and speed certainly contributes to their severity. But allowing drivers to speed on suitable divided highways does not seem to create more accidents.

So why do Americans accept the risks of passing oncoming vehicles at 110 MPH, but shudder at the idea of overtaking at the same rate on a divided highway?